Question

How do muscles move at the cellular level and respond when processed messages are received from the brain?

Hint:

Follow the nerve impulse to the muscle cell and think about what the special proteins in it do.

Answer 1

Step 1: Recall the path of the message:
The brain processes the information and sends a message along motor nerves. This message is an electrical impulse.
The motor nerve ends at a muscle, so the impulse reaches the muscle cells.

Step 2: What the muscle cell does:
When the nerve impulse reaches the muscle, the muscle cells move by changing their shape so that they shorten.

Step 3: How the shape changes:
Muscle cells have special proteins. In response to the nervous electrical impulse, these proteins change both their shape and their arrangement inside the cell.
The new arrangement of the proteins gives the muscle cell a shorter form. Many cells shortening together make the whole muscle contract and the body part moves.

Final Answer:
The muscle cells shorten when the special proteins in them change shape and arrangement after the nerve impulse arrives. \[ \boxed{\text{Muscle cells shorten as special proteins change shape and arrangement}} \]